I use a Super-Peep. Its lightweight and small and has no rubber tubing. (doesn't effect arrow speed much compared to bigger peeps and rubber tubing) The really nice thing about the Super-Peep is that the hole size is adjustable! the center is threaded, so for hunting I use the biggest size. For target shooting leagues I put in the smallest one I am cofortable with. When shooting 3D I use something in the middle. Its a very high quality peep!

Good Luck!